藏北高原D105点土壤冻融状况与温湿特征分析

Processes of Soil Thawing-Freezing and Features of Ground Temperature and Moisture at D105on the Northern Tibetan Plateau

利用CAMP/Tibet在藏北高原D105点所观测的2002年1月1日—2005年12月31日土壤温度、含水量资料,分析了该点的土壤温、湿度变化及其冻融特征.结果表明:D105点40cm深度以上土壤温度日变化明显,随着深度增加,土壤温度日变化相位明显滞后.各层土壤温度月最高值出现在8—9月,月最低值都出现在1—2月;年际气候的差异至少可以反映到185cm深处的土壤.土壤冻结和消融都是由表层开始,土壤随深度增加冻结快,消融则慢.冻结期间,土壤温度分布上部低,下部高;消融期间,则分布相反.60cm深度以上的土壤含水量在消融期有显著的波动,表明60cm深度以上的土壤与大气之间的水热交换比较频繁.土壤温度的日变化和平均温度对土壤的冻融过程有较大的影响;土壤含水量的多少会极大的影响土壤的冻融过程、土壤热量的分布状况以及地表能量的分配.因此水(湿度)热(温度)相互耦合影响着土壤的冻融过程.

Base on the ground temperature and water content data obtained in CAMP/Tibet,1st January,2002 to 31 December,2005,the features of ground temperature,moisture and soil freezing-thawing process at D105 in the northern part of Tibetan Plateau are analyzed.The results show that ground temperature above 40-cm depth existed evident daily variation,and the phase of soil temperature lagged obviously with depth.The annual maximum ground temperature was in August and September;while the minimum was in January and February.The multiannual climate variation could be recognized down to the depth of 185 cm.Soil began to freeze and thaw downwards all from the ground surface.Soil freezing velocity increased with depth,but soil thawing velocity deceased with depth.During the period of freezing,soil temperature was low at the top and high at the bottom.However,soil temperature distribution during the period of thawing was opposite to that during soil freezing period.Above the 60-cm depth,soil water content had an obvious fluctuation during the period of thawing,suggesting that frequent water and heat exchange existed between soil above the depth of 60-cm and atmosphere.The process of soil thawing-freezing were affected by ground average temperature and the daily variation of ground temperature;soil water content greatly influenced the process of soil thawing-freezing,distribution of soil heat and allocation of surface energy.Consequently,soil freezing-thawing process was affected by coupled water and heat.